1. Field of the Invention
The present invention relates to a connection structure for optical fibers, specifically to an optical fiber connector that makes an optical connection between two optical fibers without using a lens member.
2. Description of the Related Art
In connecting optical fibers, the most important technical task is to achieve a low transmission loss.
FIG. 14 illustrates a first conventional optical fiber connector 50 that has implemented a structure with a low transmission loss. As illustrated, the first conventional optical fiber connector 50 includes a cylindrical enclosure 53, and a biconvex lens 54 contained in this enclosure 53, in which one end of a first optical fiber 51 is installed in one end of the enclosure 53, and one end of a second optical fiber 52 is installed in the other end of the enclosure 53. Incident light from the one end face (not illustrated) of the first optical fiber 51 transmits through the first optical fiber to exit the other end face 51a, and, after passing through the lens 54, the light converges on the end face 52a of the optical fiber 52.
FIG. 15 illustrates a second conventional optical fiber connector 60, which includes a first cylindrical connecting part 65 with a flange 65a and a second cylindrical connecting part 66 with a flange 66a, and a first lens 63 contained in the first connecting part 65 and a second lens 64 contained in the second connecting part 66.
First and second disk-shaped fixing parts 67, 68 provided with protrusions 67a, 68a having small holes in the centers thereof are mounted onto the ends of the opposite sides to the flanges 65a, 66a of the first and second connecting parts 65, 66. One end of each of the first optical fiber 61 and the second optical fiber 62 are guided in the center holes of the fixing parts 67, 68.
First and second lenses 63, 64 are fixed inside the first and second connecting parts 65, 66, respectively, so that the optical axes coincide with each other; and thereafter, the first and second connecting parts 65, 66 are attached so that the flanges 65a, 66a are engaged with each other. The first and second fixing parts 67, 68 are fastened to the first and second connecting parts 65, 66 with screws, etc. The first and second optical fibers 61, 62 are stripped of the sheathing parts from the front ends thereof, and these ends 61a, 62a each are engaged in the center holes of the fixing parts 67, 68.
In the optical fiber connector 60 thus configured, in order to form the focuses on the end faces of the ends 61a, 62a of the first and second optical fibers 61, 62, for example, a light beam emitted from the end face of the end 61a of the first optical fiber 61 falls on the first lens 63, and goes out as a parallel beam from the first lens 63, and the parallel beam falls on the second lens 64. Then, the outgoing light from the second lens 64 falls on the end face of the end 62a of the second optical fiber 62.
However, in such optical fiber connectors 50, 60, a high positioning accuracy in the connection of the two optical fibers is required in order to transmit a stable light beam through the optical fibers. Further, in order to enhance the efficiency of optical connection through the optical elements such as the lenses and achieve a lower transmission loss than that obtained by directly connecting the optical fibers, it is necessary to fix the lenses 54, 63, 64 inside the enclosures 53, 65, 66, align the focal positions of the lenses 54, 63, 64, and adjust the positioning. Accordingly, it takes a large amount of time for the positioning adjustment.